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Subject: RE: Generators
Date: Tue, 28 Jul 2009 05:20:16 -0400
Message-ID: <A70525C94280194CAFB8EF08F63392C25E3683@USINVMAILB01.ingres.prv>
In-Reply-To: <89c0c52c0907271122i3ef820b0u3e525f29759988db@mail.gmail.com>
Thread-Topic: Generators
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From: "Alan Raison" <Alan.Raison@luminary.co.uk>
To: <dev@openjpa.apache.org>

Kevin

It is true that a field can override the default generation strategy to =
use sequences; for example I have the following sequence generator =
defined:
@SequenceGenerator(name=3D"myseq",sequenceName=3D"my_seq",initialValue=3D=
5)

And a field using this generator:
    =
@GeneratedValue(strategy=3DGenerationType.SEQUENCE,generator=3D"myseq")
    public int getColumn() { ... }

This works correctly.  However, given the field:

    @Id
    @GeneratedValue
    public int getId() { ... }

This will use the OPENJPA_SEQUENCE_TABLE unless
a) I specify (strategy=3DGenerationType.SEQUENCE), or
b) I set openjpa.Sequence=3Dnative

My dictionary does not set sequenceSQL, sequenceSchemaSQL or =
sequenceNameSQL, since it wasn't clear what these should return, but I =
have set nextSequenceQuery and overridden getSequencesSQL(String, =
String)

Is the lack of these attributes the cause for GenerationType.TABLE being =
the default?

Alan=A0

-----Original Message-----
From: Kevin Sutter [mailto:kwsutter@gmail.com]=20
Sent: 27 July 2009 19:22
To: dev@openjpa.apache.org
Subject: Re: Generators

Hi Alan,
I wonder if our documentation is in sync with the code...  The default =
value
for openjpa.Sequence is table.  But, I believe we override that if =
certain
attributes within the Dictionary are set.  For example, sequenceSQL,
sequenceSchemaSQL, and sequenceNameSQL are attributes that get set by =
data
dictionaries that support Sequences natively.  For example, DB2 and =
Oracle
are two databases that support native sequences.  And, as long as the
GeneratedValue Strategy is set to SEQUENCE, I believe this kicks in =
without
having to set openjpa.Sequence to "native".

Since you are looking to create a new dictionary for Ingres, this would
explain why you have to set the openjpa.Sequence property to get the =
desired
effect.

Can you do any experimentation to verify this?  We may need to update =
our
documentation or javadoc to make this clearer.

Kevin

On Mon, Jul 27, 2009 at 11:36 AM, Alan Raison =
<Alan.Raison@luminary.co.uk>wrote:

> Hi all
>
> I've been looking at the sequence support in DBDictionary and =
extending
> it for Ingres.  Ingres supports native sequences, but it seems that by
> default, OpenJPA prefers to use the OPENJPA_SEQUENCE_TABLE for =
internal
> sequence numbering.  Setting openjpa.Sequence=3Dnative changes this to =
use
> the native sequences.
>
> Is there a way/would it be desirable to set a preference for native
> sequences in the DB Dictionary?  I don't see this in any other
> dictionary, so I assume it's not desirable.  Perhaps this is so the
> schema is predictable?
>
> Thanks
>
> Alan
>